1. Field of the Invention
The present invention is related generally to implantable medical electrical leads. More specifically, the present invention is related to a suture sleeve for an implantable medical electrical lead.
2. Prior Art
Suture sleeves are devices that are intended to provide a means of safely and securely anchoring a medical lead inside the body. Typically, a suture sleeve is slid over a medical lead to a location where it is desired to anchor the lead inside the body. Once the sleeve is in place, sutures, which are typically stranded fibers, are wrapped around the sleeve. The sleeve is intended to provide a housing-like structure that surrounds the medical lead, preventing the suture material from contacting the lead that could potentially cause damage to the lead.
After the sleeve is secured to the lead, the suture sleeve is sewn into place in the surrounding body tissue, anchoring the lead in place. The suture sleeve, therefore, is designed to provide an anchoring structure for the lead while protecting the lead from potential damage during and after the implantation process.
One of the main problems with current suture sleeves is their lack of adequate protection from over tightened suture materials. If the sutures are tied too tight, there is an increased likelihood that the sutures could cut through the polymeric body of the sleeve and continue to cut into the lead, resulting in a damaged and impaired lead. If the suture material were to propagate through the sleeve body and further cut into the lead, the lead could possibly be fractured or even severed resulting in a malfunctioning lead. Such a damaged lead would require replacement which would add further unnecessary expense and trauma to the patient.
Suture sleeves are typically made from a biocompatible pliable polymer such as silicone rubber. This provides durability and flexibility to the sleeve and allows the suture sleeve to move with the lead during and after implantation. The silicone material is ideal for long term implantation due to its biocompatibility, flexibility, and durability properties but polymeric materials, such as silicone, are not an ideal barrier against preventing the suture strands from cutting through the silicone sleeve body and damaging the medical lead.
When the sutures are tied too tight, the suture strands cut into the polymeric sleeve material. Over time, the suture material begins to cut deeper into the sleeve, propagating through the sleeve creating cracks and splits under the stress of the tightly wound suture threads. This is especially true of silicone rubber, as once the material is cut, the slice easily propagates through the material. Eventually, the suture material propagates through the sleeve structure and begins to cut into the medical lead, destroying the anchoring structure and damaging the lead.
The reality of over tightened sutures is a major problem. There is currently no known means of controlling the force at which sutures are tightened. Every physician ties sutures with a different force every time. A suture could easily be over tightened during an emergency situation when the physician must act immediately without much thought of the force at which the sutures are tightened. Therefore, there is a need to improve the integrity of the suture sleeve to ensure that regardless of the force exerted on the suture sleeve, by the suture material, the lead is not damaged.
Rodriguez in U.S. Pat. No. 7,218,972, discusses a reinforced suture sleeve comprising a tubular body, sleeve wall and inner lumen. The tubular body is made of silicone rubber and comprises three circumferential grooves to facilitate wrapping the suture material around the outside surface of the sleeve. The sleeve wall has an inner lumen made of polyurethane which is intended to prevent an over tightened suture from cutting into the lead. According to Rodriguez, the purpose of the polyurethane inner lumen is to prevent the suture from propagating through the suture sleeve and cutting into the medical lead, thereby damaging the lead. However, such a polymeric inner lumen does not provide adequate protection from the cutting action of the suture material.
The present invention discloses a suture sleeve with reinforcement embodiments that provide superior protection from over tightened sutures while providing flexibility that enables the suture sleeve to bend and flex with the medical lead. The first reinforcement embodiment comprises a suture sleeve with an internal metallic insert that has a spiraled slot cut through its surface. The metallic insert acts as a barrier that prevents sutures from cutting into the medical lead and the spiraled slot gives the insert and resultant suture sleeve, much needed flexibility. A second reinforcement embodiment entails embedding a flexible fiber mesh into the polymeric body of the suture sleeve. The embedded fiber mesh acts as a barrier and prevents further propagation of the suture material into the sleeve while still providing flexibility to the sleeve. This embedded fiber mesh also prevents the suture material from contacting the metal insert. Therefore, the possibility that the suture material will become damaged or broken from abrading against the metal insert is reduced.
Rodriguez, unlike the present invention, does not disclose a metallic inner lumen with a spiral slot cut through the insert surface nor does Rodriguez disclose the use of a fabric mesh reinforcement embodiment that is incorporated in the sleeve body. The present invention provides increased flexibility, durability and medical lead protection that are not afforded by Rodriguez.
In a related U.S. patent application publication number 2004/0254623, Rodriquez discloses a similar suture sleeve as presented in the '972 patent, however, in this application, the polymeric sleeve insert has a variable inner wall thickness of differing geometries. As stated in the '623 application, the variable inner wall thickness is designed to provide protection from an over tightened suture as the differing geometries of the inner lumen wall compress together. The present invention, unlike Rodriguez's application, is directed to the incorporation of insert reinforcement barriers which prevent the suture material from initially cutting into the inner lumen.
Pohndorf et al. in U.S. Pat. No. 4,553,961 discloses a suture sleeve with a structure for enhancing the grip of the sleeve around the lead. The suture sleeve comprises a sleeve body made of a silicone material with a hollow passageway through the center. A cylindrical insert that provides enhanced gripping of the sleeve is molded into the center passageway of the sleeve. The inserts of various designs are intended to grip the outside surface of the lead body to prohibit movement of the sleeve along the lead.
Each of the embodiments of the cylindrical insert in the '961 patent contains horizontal slits that extend through the end of the insert. These slits as shown by Pohndorf do not provide flexibility and do not allow the sleeve to bend as provided by the sleeve reinforcement embodiments of the present invention. In addition, the slits disclosed in the '961 patent, in which the slits cut through the insert end, degrade the physical integrity of the insert, thus reducing the internal structural strength and barrier qualities of the suture sleeve.
Unlike the present invention, Pohndorf does not teach a metallic insert with a spiral slot cut through the surface of the insert. The spiral cut insert embodiment of the present invention provides a flexible barrier that stops propagation of the suture material through the suture sleeve. Pohndorf's insert embodiments lack the required structural integrity that is provided by the present invention.
Helland in U.S. Pat. No. 5,674,273 discloses an implantable pacing lead with a reinforcing sheath covering a portion of the lead body. The sheath covering is designed to prevent damage to the lead due to tightly wound sutures that cut through the sleeve body.
Helland discloses a fixture sheath comprising a spiral wound flat wire that is encased within a layer of polymer covering that is not electrically connected in the lead. Suture grooves are provided circumferentially around the sleeve in which the sutures are wrapped around. The flat wire and polymer covering are intended to stop the suture material from cutting through the sleeve body and into the medical lead, thereby causing damage to the lead.
Unlike the present invention, Helland does not disclose a spirally cut metal insert nor a flexible fiber mesh that is incorporated in the sleeve body to prevent lead damage.
Sommer et al. in U.S. Pat. No. 7,082,337 discloses a suture sleeve that comprises a hollow sleeve body with a sleeve insert that is covered with a layer of fibrous media. The suture sleeve of the '337 patent comprises a sleeve with an elastomeric insert designed with a rough surface that is embedded with a fibrous media of powder or grit of radiopaque metal, silica, ceramic or polymeric compound that is intended to prohibit physical damage to the lead.
Unlike the present invention, Sommer discloses a layer of particulate and fibrous material that surrounds the sleeve insert. This is distinctly different from the sleeve reinforcement embodiments of the present invention; specifically that of a fiber mesh that is embedded in the sleeve body itself. The design of the present invention provides a more robust barrier that protects the integrity of the suture sleeve and the medical lead. In addition, the fiber mesh embodiment of the present invention provides a degree of flexibility that allows the sleeve to bend with the lead which is not afforded by Sommer.
Therefore, what is needed is a flexible biocompatible reinforced suture sleeve that prevents damage to the implanted medical lead, suture material, as well as inhibits damage to the anchoring suture sleeve.